High speed control valve for hydraulic drives

ABSTRACT

AN IMPROVED HYDRAULIC DRIVE WITH A RECIPROCATING WORKING PISTON WHOSE SIDE REMOTE FROM THE LOAD MAY BE AFFECTED BY A LIQUID OR GASEOUS PRESSURE MEDIUM, AND COMPRISING A CONTROL VALVE WITH AN AXIALLY DISPLACEABLE CONTROL SLIDE, ADAPTED TO MOVE IN A CONTROL SLEEVE WITH RADIALLY DISPOSED INLET AND OUTLET ORIFICES, WHEREIN THE IMPROVEMENT COMPRISES ADAPTATION FOR HIGH OPERATING FREQUENCIES IN THAT THE CONTROL SLEEVE IS AXIALLY DISPLACEABLE IN THE VALVE HOUSING AND IS DIRECTLY CONNECTED WITH THE PISTON, AND BY PROVIDING A REVOLVING CAM FOR PERIODICALLY MOVING THE SPRING-LOADED PISTON SLIDE.

United States Patent inventor Jan Willem Hilbrlnds l-lattingen, (Ruhr) Germany Appl. No. 746,137 Filed July 19, 1968 Patented June 28, 1971 Assignee Maschinenlabrik Koppern & Co. KG,

Hattingen, (Ruhr! Germany Priority July 20, 1967 Germany HIGH SPEED CONTROL VALVE FOR HYDRAULIC DRIVES 8 Claims, 2 Drawing Figs.

US. Cl. 91/39, 9l/165,9l/378,9l/417 Int. .....F15b 21/02, F15b 15/17 Fieidoiseareh 9l/39,417;

91/378, 374 (Cursory) [56] References Cited UNITED STATES PATENTS 2,447,090 8/1948 Pollock 91/374 2,644,427 7/1953 Sedgfield et al. 91/378 719,109 1/1903 Hanson 91/39 1,822,667 9/1931 Proell 91/39 2,055,530 9/1936 l-lallenbeck 91/39 Primary Examiner-Paul E. Maslousky Attorney-Christen and Sabol ABSTRACT: An improved hydraulic drive with a reciprocating working piston whose side remote from the load may be affected by a liquid or gaseous pressure medium, and comprising a control valve with an axially displaceable control slide, adapted to move in a control sleeve with radially disposed inlet and outlet orifices, wherein the improvement comprises adaptation for high operating frequencies in that the control sleeve is axially displaceable in the valve housing and is directly connected with the piston, and by providing a revolving cam for periodically moving the spring-loaded piston slide.

PATENTEUJUHZEBIQTI 3,587,394

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JAN W/LLEM MIL BRA/v05 BY M ,JW vfl fluuv ATTORNEY PATENIEU JUH28 19?:

SHEET 2 BF 2 liilllGllll MMZD CONTROL VALVE FUR HYDRAULIC DMVES Hydraulic drives with reciprocating pistons of the type mentioned above are generally known and used. In these constructions, the piston is returned to its starting position by the load, or by a spring. or by admitting the liquid or gaseous pressure medium to the side of the piston facing the load. Drives of this type operate reliably at low operating frequencies, even where the control member is automatically operated. Other hydraulic drives are known for fatigue machines and similar applications, operating at high frequencies, for example of the order of 20 cycles per second. These known drives operate with complicated valve controls with electronically controlled ser vovalves.

It is an object of the invention to provide a hydraulic drive of the type hereinbefore mentioned, capable of operating at high frequencies, equipped with a simple automatic control, and in which the working piston can be kept within a predetermined operating range without the use of limit stops.

Such drives are required, for example, for crushers, vibrators, and generally for machines operating at high frequencies.

It is a further object of the invention to provide a hydraulic drive, in which the control bush is mounted axially displaceably in the valve housing and is connected directly with the working piston, and which comprises a revolving cam for periodically axially displacing the piston slide which is spring loaded in the direction of the cam.

it is a further object of the invention to provide a hydraulic drive of the kind hereinbefore mentioned, in which the valve housing is flange mounted coaxially to the working piston to its housing.

The control bush may be flange mounted directly on the working piston. However, in order to produce a larger working surface, the control bush and the working piston may be connected by means of a connecting rod.

it is a further object of the invention to provide hydraulic drive of the kind hereinbefore mentioned, in which the end of working piston facing the load is provided with an annular shoulder, the surface of which is smaller than the working surface on the opposite side of the working piston, and wherein the annular space is connected with a source of the pressure medium.

The invention will be further described by way of example, with reference to the accompanying drawing in which:

FIG. ll shows a longitudinal cross section of a hydraulic drive according to the invention, and

FIG. 2 shows a modified form of the invention.

A working piston 2 is arranged in a cylinder 4 closed by a cover 6 and a further cover s.

The working piston 2 is equipped with a piston rod 10 passing through the cover 6 and having a smaller diameter than the working piston, so that an annular chamber 112 is formed in the cylinder 2 and provided with a connection for the pressure medium. in the embodiment shown, the cover 8 is the connecting flange of a valve housing to mounted coaxially to the working piston.

A control bush Ed is mounted axially displaceably in the valve housing to and is flange mounted on the adjacent side of the working piston 2. A control slide is axially displaceable in the control bush 1d and is provided with an extension 22 passing through a bore in an end cover 24 of the valve housing 116.

The valve housing 16 is equipped with a pressure medium connection 24 leading to a groove 26 on the inner periphery of the housing. in the zone of the groove 26 the control bush 18 has radial bores leading to a peripheral groove 28 on the inner surface of the control bush m. The control slide 20 has a control edge 30 cooperating with the groove 28.

An oil reflux connection 32 is provided at the opposite end of the valve housing and terminates in an annular groove 34 extending to the cover 2d of the valve housing. The control bush Ed has radial bores leading into the annular groove 34 and communicating with an annular groove 36 on the inner periphery of the control bush. This annular groove cooperates with a further control edge 38 of the piston slide 20 which is opposite the control edge 30.

Between the control edges 30 and 38, the piston slide is shouldered so as to form an annular chamber 40. This annular chamber communicates through radial bores 42 with an annular groove on the inner periphery of the valve housing l6. From this annular groove 44 axial bores 46 lead to the cylinder chamber 48 on the side of the working piston 2 opposite the piston rod It). The axial height of the annular grooves 26, 3d and M correspond at least to the maximum travel of the working piston 2 between its extreme end positions.

The end chamber 50 of the control bush 1d communicates through a piston bore 52 with the annular groove 34 as known in the art.

A threaded pin 54 is screwed into the end of the extension 22 of the piston slide 20. A spring plate 58 is mounted on the end of this extension by means of a nut 56. A compression spring 60 is fitted between the spring plate 58 and the cover 24 ofthe valve housing.

The end of the threaded pin 54 cooperates with a revolving cam 62 which revolves at a speed which is preferably adjustable. The drive just described is supplied with hydraulic fluid through a hydraulic system comprising a pump 64, an over pressure valve 66, and a pressure accumulator 68, via a line leading to the connection 2d. A conduit 72 connects the pressure oil supply for the annular chamber 12 with the conduit 70. The conduit 72 incorporates a pressure reducing valve 74, an over pressure valve 76, and a pressure accumulator 78. A nonretum valve d0 prevents the reverse flow of the oil. The cylinder 4 is connected to the connection 14 by means of a conduit 82.

The drive hereinbefore described operates as follow:

The cam 62 moves the piston slide 20 towards the left and admits the hydraulic oil from the annular groove 28 through the conduit M to the cylinder chamber 48. In consequence the working piston 2 is moved towards the left against the action of the load. During this the control piston of the control bush l8 advances at high speed so that the full flow cross section is available practically at once for the hydraulic oil.

Under the pressure of the spring 60, the control slide 20 moves to the right as soon as the point of the cam 62 has passed. The working piston 2 and the control bush 18 continue to move to the left until the annular groove 28 has been covered by the control edge 30. Then the control slide 20 continues to move to the right and the control edge 38 opens the annular groove 36 enabling oil to leave the cylinder chamber d8 and the annular groove 34 through the dotted line return conduit 33 under the action of the load. The working piston 2 and the control bush 18 move to the right until the angular groove 36 has again been covered by the control edge 38. Then the operating cycle just described is repeated. As may be seen from the preceding description, the operating frequency depends, under the assumption of sufficient flow cross sections, only on the rotational speed of the cam 62. The working piston moves between predetermined terminal positions without the provision of limit stops.

The operating range may be adjusted by adjusting the threaded pin 54.

In the embodiment shown the returning action of the load is supported by the effects of the pressure medium on the piston in the cylinder chamber 12 so that. the drive operates as described also in the absence of a load. Since only the returning forces must be applied in the cylinder chamber 12, the pressure in this chamber 12 may be substantially lower than in the cylinder chamber 48. The working pressure for returning the working piston may be adjusted by means of a pressure reducing valve 76. The use of reduced pressure raises simultaneously the effective work performed by the pressure medium in the cylinder chamber M.

The ratio between working stroke and return stroke may be determined by the shape ofthe cam 61..

The working range of the working piston described above, will also be maintained if the piston is temporarily effected by an overload, that is to say it cannot carry out its full travel during the working stroke. In this case, after the elimination of the overload, the piston will resume its predetermined working range after a few working cycles.

As may be seen from the drawing, in the embodiment shown the size of the affected surface in the cylinder chamber 43 is limited by the outer diameter of the control bush w as a function of the necessary flow cross sections within the valve arrangement. As shown in FIG. 2 an increase in the working surface area may be achieved by connecting thecontrol bush 18 with the working piston 2' by a connecting rod l9, which may have a comparatively small diameter. The cover 8 of the valve housing has in this case a closed base 9 through which the connecting rod passes in sealed relationship thereto by means of an opening therein provided with a seal ll. The chamber 13 formed in front of the control bush lfil is connected with the end chamber 50 via conduit 13 and thereby with the oil return conduit 33 via conduit 52 in the control slide and the connection 32. The other features of this form of control valve correspond to those of the valve shown in FIG. 1.

lclaim:

l. Hydraulic drive means comprising reciprocating working piston means and control valve means, housing means including cylindrical chamber means for the working piston means and valve chamber means for the control valve means, said valve means including control bush means slidably positioned in said valve chamber means and connected with the working piston means for concurrent reciprocating movement with the working piston means and also including control piston means positioned in said valve chamber means for reciprocating movement in a path parallel with the path of movement of the control bush means and in sliding contact therewith, said valve chamber means having inlet means for fluid under pressure, conduit means communicating with the cylindrical chamber means for delivering fluid to one side of the working piston means only and outlet means for fluid returned from said cylindrical chamber means, fluid supply means for delivering fluid under pressure to said inlet means and to the opposite side of the working piston means, said control piston means having an axially elongated medially arranged recessed portion in fluid tight engagement with said control bush means to provide an axially elongated fluid chamber in cooperation with said control bush means, said control bush means being provided with three axially spaced ports, one of said ports establishing communication between said elongated chamber and said conduit means in all positions of said drive means, a second of said ports establishing communication between said elongated chamber and said outlet means when the control piston is displaced in one direction with respect to the control bush, the third port establishing communication between said elongated chamber and said outlet means when the control piston is displaced with respect to the control bush in the opposite direction, the axial distance between said second and third ports being no less than the length of said recessed portion of the control piston means whereby only one of said lastmcntioned ports can be in communication with said elongated chamber at the same time, means to regulate the effective application of force against said working piston means so that the force of fluid applied to said one side will exceed the force of fluid applied to said opposite side, and cam means and spring return means for reciprocating said control piston means to control the rate of movement of the working piston means.

2. Hydraulic drive means as defined in claim 5, wherein said control bush means includes a cylindrical element secured to said working piston means in axial alignment therewith; and said control piston means is coaxially slidably mounted within said cylindrical element, said control piston means having an annularly reduced medial portion to provide said elongated chamber said three axially spacedports extending radially through said cylindrical element, said one of the ports being positioned axially between the second and third ports.

3. A drive as set forth in claim 2, wherein the valve housing (i6) is flange mounted on the housing of the working piston (2) in coaxial relationship therewith.

4. A drive as set forth in claim 2, wherein the control bush (18) is directly flange mounted on the working piston (2).

5. A drive as set forth in claim 2, wherein the control bush (i8) is connected to the working piston (2) by means ofa connecting rod.

6. A drive as set forth in claim 2, wherein the end of the working piston (2) facing the load has an annular shoulder the surface of which is smaller than that on the other side of the working piston, and wherein the annular chamber (12) at the end of the working piston facing the load communicates with a source of pressure medium (78) whose pressure is lower than the pressure prevailing in the opposite cylinder chamber.

7. A drive as set forth in claim 2, comprising an annular shoulder at the end of the working piston facing the load, with a surface smaller than the working surface on the other side of the working piston, and wherein the annular chamber on the side of the working piston facing the load communicates with the source of pressure medium, wherein the working pressure in the annular chamber facing the load is smaller than in the annular chamber remote from the load.

8. A drive as set forth in claim 2, wherein the control slide carries, at its end cooperating with the cam (62) a pressure plunger 54, the axial position of which is variable. 

